I'm watching and wondering which of my four POL pullets is going to turn out to be the boss.
At first I thought it would be Violet the Bluebell (bigger, redder comb, outgoing personality) and that Lily Leghorn would be bottom of the ranking (very small bird, quiet, kept to the background.) But Lily was first to lay and had produced 9 eggs before Violet laid any, and yesterday I saw Lily give Violet a really hard peck which made her squawk,and tipped her off the perch. In my previous flock, Nutmeg, the small CLB, ruled 2 or 3 generations of hens bigger than she was, once the adult hens who were there before she came had died off. And a long time ago, I had a tiny Silky, Matilda, who quickly taught a new flock of 8 huge RIR pullets who was in charge.
So size doesn't necessarily seem to be a determining factor. Actually I have a hunch that it's brains and personality rather than brawn. Both Matilda and Nutmeg more than made up for their small size by obvious intelligence and leadership qualities. Nutmeg was brought up alongside Marigold, my Buff Sussex, as chicks, and it was really funny watching her telling and showing Marigold what to do, where to do it, and when. I know from experience with horses and ponies that the smaller ones are much more intelligent than the large breeds, probably because they come from wilder stock which need their wits to survive on Exmoor, Dartmoor, the Welsh mountains etc. Maybe it's the same with hens?
So, supposing you start off with a mixed-breed flock of POL pullets, all the same age, in a new location, and observe them as they settle down together over the next few weeks. What do you think are the factors which are likely to determine the order of precedence? Size? Early maturity? Breed? If the new flock has both hybrids and purebreds, will the likely difference in age at first egg give the hybrids an edge?
Of course this assumes a single-sex group. If there a cockerel, then a lot of other factors come into play - which I know nothing about.

I like that intelligence test for chickens. Aerial is my brightest but also the oldest and, as it happens, the boss. Bonnie isn't very clever and neither is Linden - they will even walk over to the open door after pacing back and forth along the side of the run wishing to get out. Get to the door then catch sight of a hen outside pecking at the desired treat and run hopefully away from the door again towards the side of the coop, repeat!
They learn the trick in time, of course, but it would be interesting to try the unfamiliar box test Chris surgessted.